基于图像测速的薄壁堰流表面流场测量方法

A new method for reconstructing velocity field in weir flow based on binocular stereovision and particle image velocimetry

针对薄壁堰流水面落差大、流速沿程变化剧烈的特点,提出一种测量堰流表面三维流场的有效方法。该方法基于双相机共面法重构水面形态(无需对相机进行复杂的内外参数标定)和大尺度粒子图像测速技术(LSPIV)测量二维流场,通过相机像平面与水面之间的空间映射关系,将像平面的二维流场数据逆投影至世界坐标系下已知坐标点的切平面上,解算出三维表面流场。该方法应用于薄壁堰流试验,有效重构了堰流三维表面形态及流场,其初步结果表明,堰流的流向速度在自由泄流长度范围内先增加后减小,转折点大致在自由泄流长度中间位置;在该位置之后,垂向流速占主导;同时该方法可行,计算结果合理。

We propose a new method for reconstructing complex surface velocity field in weir flow which is notoriously difficult to measure due to its sharp drop and high fluctuation. The new method is able to map the curved flow surface by two coplanar cameras and achieves measurement of two-dimensional velocity field through large-scale particle image velocimetry（ LSPIV）. The measured two-dimensional velocity field is projected onto the three-dimensional flow surface based on complex linear mapping relationship between the object space and image space. Application of the method to weir flow measurement yields satisfactory results,showing that the longitudinal velocity turns in trend from increase to decrease at the middle point of nappe,while the vertical velocity increases all the way along the nappe and plays a dominant role in the lower half of the nappe.